Fishing boats and vessels are often equipped with a trolling motor for providing a relatively small amount of thrust to slowly and quietly propel the boat or vessel while the operator is fishing. The motor is typically mounted to the bow of the boat (alternatively the motor may be mounted at other locations in the boat, for example the motor may be transom mounted at the stern of the boat) so that the thrust pulls the boat through the water. The power source for the trolling motor is usually a lead-acid marine battery having a limited capacity measured by the amount of amp-hours that the battery is capable of providing. The limited battery capacity limits the combination of trolling motor speed and time available to the fisherman. For a predetermined state of charge on the battery, the fisherman can troll for a relatively long amount of time at low speed (i.e., low-power usage), or for a relatively short amount of time at high speed (i.e., high-power usage). When the battery is discharged, the fisherman needs to stop his trolling operations until such time that the battery can be charged. Unfortunately, prior art trolling motors do not provide these fisherman with a reliable way of determining how long the battery will last until it needs to be recharged. Thus, the fisherman may find that the battery power is depleted well before the end of the fishing day.
Some trolling motors provide information related to the trolling motor battery condition, to the operator, by measuring and displaying the percentage charge of the battery. The display may be in the form of a bar graph having a number of segments corresponding to the percentage of charge (e.g., four out of ten segments may be lighted to indicate a 40 percent charge), or alternatively the display may be in a numerical percentage charge of the battery. Based on the display, an operator may attempt to roughly estimate the amount of running t me remaining based on his prior experience with the boat and trolling motor at different operating speed conditions. The display, however, does not provide an accurate indication of the amount of running time remaining before the battery will be discharged. This defect results from the fact that the amount of current drawn from the battery will depend on the speed settings of the trolling motor. As the speed setting, and thus propeller speed, changes, the current usage will vary in a very wide range (e.g., from 1 amp to 50 amps). Thus, for example, a 40 percent charge may last two hours with the motor operating at its maximum speed, but may last for eight hours if the speed is cut back to a slower trolling speed. Therefore, even an experienced operator will be able to make only a very inaccurate estimate of the amount of running time left using existing battery gauges, and will only be able to guess what speed setting will correspond to the amount of time that he wishes to continue trolling.
Accordingly, there is a need for an improved battery gauge for an electric trolling motor which determines the amount of running time remaining at the current speed setting of the trolling motor before the battery loses its charge, and displays this running time. Further, there is a need for a battery gauge in which the operator will know how much longer he may continue to troll at the current speed setting. Further still, there is a need for a battery gauge for an electric trolling motor which provides information of which the user can use to adjust the speed setting to decrease the current draw and conserve battery power if insufficient running time is available at the current speed setting, avoiding the possibility of running out of battery power too early.